1. Field of the Invention
This invention relates to mechanical devices, such as filters and dampers, made from large wire ( greater than 0.025xe2x80x3 diameter) loops, and to methods for making the same.
2. The State of the Art
Knitted wire mesh is used for a wide variety of articles, from scrubbing pads to filters for the hot gases generated when airbags deploy to mechanical dampers. These meshes are made on knitting machines designed for using wire instead of thread, and so the devices have very strong needles around which the wire is wrapped as it is knitted. These knitting machines can only operate on wire having a diameter up to about 0.030xe2x80x3 (about 0.762 mm); thicker wire diameters induce stress cracks in the needles of the knitting machines, causing them to break.
There are applications for wire mesh structures, such as in airbags and mechanical dampers (energy absorbers), where the use of a larger diameter wire would be more useful. A larger diameter wire provides increased mass for cooling the hot gases released from the gas generating charge in airbag cans, and increased strength for withstanding the blast when the gas is generated. Likewise, a larger diameter wire provides increased strength and resistance to deformation for mechanical dampers made from wire mesh. Thus, larger wire diameters absorb more energy, both thermal and kinetic, and sustain filter integrity during the explosive deployment of the airbag because it takes longer to reach a temperature where the material begins to degrade.
In light of the foregoing, one object of this invention is to provide a large wire loop mesh for such applications as airbag filters and mechanical dampers. Another object of this invention is to provide such devices with wires of at least 0.025xe2x80x3 (about 0.6 mm), more preferably at least 0.028xe2x80x3 (about 0.7 mm), and most preferably at least 0.035xe2x80x3 (about 0.9 mm) in diameter, although the invention can be used with any wire diameter. Yet another object of this invention is to produce such devices without the use of present wire knitting machines that are limited in the size of the wire that can be knit.
In summary, this invention provides a large wire loop having at least two layers of wire suitable for forming into a wire mesh device wherein the wire in the loop is preferably greater than 0.028xe2x80x3 in diameter, most preferably greater than 0.035xe2x80x3 in diameter. Also provided is an article made from large wire loop that has been formed in a mold.
In another embodiment, this invention provides such large wire loops by the process of wrapping a large diameter wire around a mandrel, removing it from the mandrel, flattening the tubular wire loop, and forming the flattened wire loop into the desired device in a mold.